DE102004024375B4 - Knock detection device and detection method - Google Patents

Abstract

A knock detection device comprising: spark plugs disposed in cylinders of an internal combustion engine; ion current detecting means (2) for detecting ion currents flowing in the spark plugs; time / frequency transforming means (3) for sampling the ion currents at time intervals to determine time / frequency components (Cn (f)) of the sampled ion currents using a short-term Fourier transform, the time intervals having one or more overlaps within allow a time from after ignition by one of the spark plugs until a spark plug ignites next in the own cylinder or in another cylinder.

Description

BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates to a knock detection apparatus and a detection method that detects, with high accuracy, the presence of knocking and its occurrence in time from changes in ion currents detected when using spark plugs at the time of combustion in an internal combustion engine.

Description of the Prior Art

It is known that when fuel is combusted in the cylinders of an internal combustion engine, ions are generated, and that these ions can be measured as ion currents by attaching probes which apply a high voltage to the interior of the cylinders. Because knocking vibration components are superimposed on the ion currents when knocking occurs in an internal combustion engine, the occurrence of knocking can be detected by detecting these vibration components. However, in the case where the noise of the spark plug containing many frequency components is superposed on the ion currents, this noise is finally detected as vibration parts of knocking, and it is mistaken for knock, even if it does not occur at all.

As a method for avoiding this disadvantage, the following technologies have been disclosed. For one thing is in the in the Japanese Patent No. 3184451 (Pages 2 to 3, 1 and 2 ) technology has provided a band-pass filter which filters out only the frequency components of the knock that are superimposed on the ion currents when a knock has occurred, and a noise-rejection band-pass filter that passes through frequency components different from the frequency components of the knock. So z. For example, by a blocking switching device when a noise resulting from the operation of an injection system is detected by the noise suppression band-pass filter, a knock signal is not input to a determination circuit.

At the in JP-A-11-2175 (Pages 3 to 4, 1 and 3 According to the technology disclosed, signals based on the ionic currents are passed through a high pass filter, then knocking signals are passed through a filter that passes through a particular frequency band, only the noise component is recovered separately through a filter that blocks the particular frequency band both are held peaked, digitally converted and imported into a controller, both signals are compared by the controller, and it is determined whether knocking occurs or not based on the compared signals.

It is also in JP-A-61-57830 (Pages 3 to 4, 1 and 3 ) discloses a technology in which signals passing through a filter that is selectively traversed by signals based on the ion currents undergo knocking signals and signals that pass through a filter that are unique to those produced by the mechanical dimensions of each cylinder Selectively transmitting vibration frequencies each time over a predetermined period of time, signals are obtained from the ratio of the respective integrated values to detect the occurrence of knocking, and the signals are integrated over a predetermined number of revolutions, thereby determining the knocking is performed.

It is also in JP-A-11-295188 (Pages 5 to 8, 9 to 11 ) discloses a technology in which ions-based signals are passed through a high-pass filter and a low-pass filter, extracting only one knock-detection payload, passing the knock-sense payload through an A / D converter, then a discrete Fourier transform is subjected to, the frequency is analyzed, it is determined from the result of the analysis, whether the signal originates from the knocking or the noise, and the running state of the internal combustion engine is determined.

As described above, these various technologies have been disclosed. In the case of Japanese Patent No. 3184451 however, even if it is detected as a signal containing the knock component, a signal is judged unfounded when a spark noise signal is included, and it is erroneously determined that knocking does not occur even if it is. Also, the ionic currents are signals that are small depending on the running state, and the noise signal becomes coarse when the operating sound of the fuel injection system and external noise are superimposed as by a telephone, so that with the methods of JP-A-11-2175 and JP-A-61-57830 a knock can not be fully detected.

Furthermore, from the US 5,687,082 A It is known to subject an ignition voltage, an ignition current or even an ignition impedance of a combustion engine to a systematic analysis in which a recorded measurement profile is examined for its quality. A measure of the quality can be determined, for example, from a typical measurement process of a knock signal or that of a misfire. According to one embodiment of the According to the invention, the quality can also be determined by means of a Fourier analysis or a wavelet analysis. On the basis of the determined process quality, the ignition behavior can be influenced by means of a feedback control.

The publication EP 1 221 603 A1 teaches a sensor-based detection of a regular course of a combustion process in an internal combustion engine. A vibration frequency analysis in this case allows the determination of combustion anomalies by the vibration frequency structure is compared with predetermined values. An analysis of the time course also allows to determine which cylinder in the internal combustion engine has the detected anomaly.

An alternative form of determining anomalies of a combustion process in an internal combustion engine describes the EP 1 134 386 A2 , There, the time course of the piston pressure with the curve of the angle of the piston rod before and after an engine ignition are compared, and obtained from the comparison conclusions about a combustion abnormality.

From the aforementioned documents and the further known documents "Sensorless Speed Measurement of AC Machines Using Analytical Wavelet Transform", Aller, Habetler, Harley, Tallam, Lee, IEEE Transaction on Industry Applications Vol. 5, "Effectiveness of the continuous wavelet transform in the analysis of some dispersive elastic waves", Kim and Kim, J. Acoust. Soc. At the. 110 (1) and "Two steps phase shifting algorithm using analytic wavelets", Almazán-Cuéllar, Malaccra-Hernández Severin, Optics Communication 212 (2002) 71-84 numerous instructions with respect to a frequency analysis, in particular with regard to a wavelet analysis are known , Nevertheless, such analyzes have the problem that in the determination of anomalies in the ignition voltage and high-frequency components in the measurement process occur, which can not be detected due to the length of the required analysis intervals and thus can not be assigned or assigned incorrectly. Consequently, an advantageous influence on the ignition behavior of the internal combustion engine is not sufficiently possible.

Also, in the prior art, as a specification for the detection, time intervals are used wherein the intervals between the individual ignitions are used as units in relation to the knock detection, and knock, which is a phenomenon occurring and disappearing in units of time shorter than these intervals are can not be detected accurately. For this reason, there was a problem that control methods could not be reconciled with the timing of knocking. In addition, there were problems that the determination function was too much responsive to ion current signals whose amplitude was increased due to the influence of additives added to the fuel, and due to which impulse noise superimposed on the ion currents contained many frequency components. Also, in all the prior art examples, the accuracy of knock determination was low because the temporal resolution was low.

SUMMARY OF THE INVENTION

The present invention has been made to solve these problems, and its object is to detect with high accuracy the occurrence of knocking and its timing with units of time shorter than intervals between firings, even in the case of in which the ion currents generated in the cylinders of an internal combustion engine are measured and noise is superimposed on the ion currents.

A knock detection device relating to the invention comprises: spark plugs arranged in cylinders of an internal combustion engine; an ion current detecting means for detecting ion currents flowing in the spark plugs; time / frequency transform means for sampling the ion currents at time intervals to determine time / frequency components of the sampled ion streams using a short time Fourier transform, the time intervals one or more intersections within a time from after ignition by one of the Allow spark plugs until next ignites a spark plug in its own cylinder or in another cylinder.

Furthermore, a knock detection device relating to the invention comprises: spark plugs arranged in cylinders of an internal combustion engine; an ion current detecting means for detecting ion currents flowing in the spark plugs; time / frequency transform means for sampling the ion currents at time intervals to determine time / frequency components of the sampled ion streams using a Gabor wavelet transform, the time intervals covering one or more intersections within a time from after ignition by one of the allow the spark plugs until next ignites a spark plug in its own cylinder or in another cylinder.

A knock detection method relating to the invention comprises: detecting ion currents using spark plugs arranged in cylinders of an internal combustion engine; Put by Time intervals which permit one or more overlaps of respective time intervals within a time from after ignition by one of the spark plugs until next a spark plug ignites in its own cylinder or in another cylinder; Sampling current values of the ion currents in the respective time intervals, performing a time / frequency transformation on the sampled current values of the ion currents, and determining the time / frequency components of the ion currents; and detecting knock based on the time / frequency components of the sampled ion streams and a running state of the internal combustion engine, and controlling the time / frequency transformation to obtain the time / frequency components of the sampled ion streams using a short-time Fourier transform to determine.

Further, a knock detection method relating to the invention comprises: detecting ion currents by using spark plugs arranged in cylinders of an internal combustion engine; Setting time intervals that permit one or more overlaps of respective time intervals within a time from after ignition by one of the spark plugs, until next a spark plug ignites in its own cylinder or in another cylinder; Sampling current values of the ion currents in the respective time intervals, performing a time / frequency transformation on the sampled current values of the ion currents, and determining the time / frequency components of the ion currents; and detecting knocking based on the time / frequency components of the sampled ion streams and a running state of the internal combustion engine, and controlling the time / frequency transformation to determine the time / frequency components of the sampled ion streams using a Gabor wavelet transform ,

BRIEF DESCRIPTION OF THE DRAWINGS

1 Fig. 10 is a block diagram showing the schematic construction of a knock detection device and a knock detection method according to a first embodiment of the invention;

2 Fig. 12 is a block diagram describing the ion current scanning in the knock detection device and the detection method according to the first embodiment of the invention;

3 FIG. 10 is an explanatory graph of ion current detection intervals in the knock detection device and the detection method according to the first embodiment of the invention; FIG.

the 4A . 4B and 4C are explanatory curves of time / frequency transformation and knock determination function values in the knock detection device and the detection method according to the first embodiment of the invention, respectively; and

the 5A . 5B and 5C 11 are explanatory graphs of time / frequency transformation and knock determination function values in a knock detection device and a detection method according to a second embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First embodiment

1 to 4C FIG. 15 are diagrams describing a knock detection device and a detection method according to a first embodiment of the invention. FIG. 1 FIG. 12 is a block diagram showing the schematic structure of the knock detecting device and the detecting method; FIG. 2 is a block diagram describing ion current scanning 3 FIG. 4 is an explanatory graph showing sampling intervals in ion current detection, and FIG 4A . 4B and 4C are explanatory curves describing the result of time / frequency transformation of ion currents and knock determination function values.

In 1 includes an ignition device 1 a well-known ignition circuit, and an ion current detection device 2 detects an ion current from the current of a secondary ignition circuit and is a well-known ion current detection circuit. As will be described below, the time / frequency transform means 3 a Fourier transform, so that a knock can be determined from an ion current signal, and a knock detection device 4 represents the presence of the knocking from the result of the transformation by the time / frequency transformation means 3 fixed and recorded the time course of knocking.

A detection controller 5 enters the running state of an internal combustion engine, controls the time / frequency transformation device 3 and the knock detection device 4 , and according to the running state of the internal combustion engine, transforms sampling times of ion current values resulting from the time / frequency transformation device 3 and / or a number of ion current samples which serve as the default for the time / frequency transformation. The result of the detection by the knock detection device 4 is sent to an ignition controller 6 forwarded, and the ignition control device 6 performs the control of ignition timing according to the status of the knocking.

The time / frequency transformation means 3 includes an in 2 shown ion current scanner 7 and a transformation device 8th for the sample of the ionic current. The time / frequency transformation means 3 first determines ion current samples x (0), x (Δt), x (2Δt), ... from the detected ion currents with respect to 0, Δt, 2Δt, ..., the times of set intervals from one of the detection control means 5 certain starting point. In this embodiment, a case where Δt = 5μ is used as an example, however, Δt may be optionally set depending on the prevailing conditions.

Next, the time / frequency transform means determines 3 the time / frequency components Cn (f) in the time intervals from the ion current samples included in the time intervals In = (Tn, Tn + ΔT, ..., Tn + (M-1) ΔT) thus set, that an overlap is allowed by the detection control device 5 is fixed. Ie. that here, as in 3 shown, the time / frequency transformation means 3 Sets time intervals that one or more overlaps in time from the by the detection controller 5 allow certain ignition until its own cylinder or other cylinder ignites, it samples the current values of the ion currents with respect to each time interval and determines their time / frequency components. In the present invention, an example is described in which M = 256 and T _{n + 1} = T _n + (M / K) ΔT (where K = 8 and n = 0, 1, 2, ...), but the Effectiveness of this embodiment is not limited to these values.

The specific manner of determining the time / frequency components employs a short-time Fourier transform using a Hanning window W (m) having an order M defined by the following equation as an example of this embodiment, but wherein FIG Effectiveness of the invention is not limited to this selection of the window function.

[Equation 1]

• W (m) = {1 - cos [2π (m + 1) / (M + 1)]} / 2 (1)

Here m (0, 1, 2 ... M - 1), and with reference to the real number x, the symbol cos (x) represents a cosine function of x and the symbol n represents Pi.

With respect to the set time intervals In, the time / frequency components Cn (f) (where f = 0, 1, 2 ... M-1) are determined by the following equation.

[Equation 2]

• Cn (f) = Σ {0≤m≤M-1} {x (Tn + mΔT) w (m) exp (-2πifm / (M-1))} (2)

Here, the symbol i stands for an imaginary unit, and with respect to the complex number x, exp (x) represents an exponential function of x. Further, with respect to the sequence {a (m)}, the symbol Σ {0 ≤ m ≤ M - 1} {a (m)} is an operation corresponding to the sum a (0) + a (1) + ... + a (M-1) of the sequence.

Hereinafter, with respect to the logical expression f (x) and the sequence a (x), Σ {f (x)} {a (x)} represents an operation corresponding to the sum a (x ₀ ) + a (x ₁ ) + ... + a (x _k ) (where {x ₀ , x ₁ , x _k } is a set of numbers satisfying the logical expression f (x)) of succession with the set of x where the logical expression f (x) becomes true.

The knock detection device 4 does not need all time / frequency components. Because of the condition that the original ion current samples are real numbers, all the time / frequency components Cn (f) (where {f = 0, 1, ... M-1}) are not independent. In the time / frequency transformation means 3 For example, the time / frequency components Cn (f) are determined only with respect to the value of f that the detection controller 5 determined and the for the knock detection device 4 necessary is.

It is well known that tapping causes vibrations which, as primary components, have frequencies determined by shape, pressure, temperature and molecular weight within the cylinders. Of these frequencies, the frequencies at which the amplitude in the experiment reaches a maximum value are taken as primary frequency f0, and the frequencies on either side of where the amplitude in the experiment reaches a minimum value are referred to as f ^- hergenommen and f ^+. In this embodiment, only the time / frequency components Cn (f0), Cn (f ^- ) and Cn (f ⁺ ) are calculated with respect to f0 = 5, f ^- = 3 and f ⁺ = 9, but it is also possible to change this selection according to the running state. Also, the effectiveness of the invention is not limited to these values.

When knocking occurs and vibrations are caused, the absolute value | Cn (f0) | the primary vibration component a large value. Below is the character | x | for the absolute value of x. But it can also take a large value when the ion current is superimposed on a pulse noise. Thus, in the knock detection device 4 calculated the following equation of determination.

[Equation 3]

• D (n) = (2x | Cn (f0) | - | Cn (f ^- ) | - | Cn (f ⁺ ) |) (3)

While this value takes a large positive value with respect to the ion current samples when a vibration caused by knocking occurs, it is possible to suppress the influence thereof when the ion current values are generated from the impulse noise. However, if the ion currents themselves are increased by additions, this equation of determination is proportional to the ion current intensity coefficient, which is their gain. In order to prevent an erroneous determination stemming from this influence, the determination equation is divided by a standard factor C defined by the following equation.

[Equation 4]

• C = [Σ {0 ≤ f ≤ M / 2 - 1} {| Cn (f) | ² }] ^(1/2) (4)

Here, with respect to the complex numbers x, y, the expression x ^{y stands} for the function of x y.

In this way, there is obtained a determination function E (n) whose insensitivity to the superposition of a pulse noise and changes in the ion current intensity coefficient is high, by the following equation.

[Equation 5]

• E (n) = (2x | Cn (f0) | - | Cn (f ^- ) | - | Cn (f ⁺ ) |) / [Σ {0 ≦ f ≦ M / 2 - 1} {| Cn (f) | ² }] ^(1/2) (5)

In the present embodiment, the above determination function value is compared with a preset threshold Th; However, the determination function can also be determined by a similar function, which corresponds to the resolution principle described above.

The 4A . 4B and 4C show results, specific data being used in this embodiment. In the 4C determination function values shown are from the in 4A ion current can be obtained, and knocking can be reliably detected by making the threshold threshold Th become 0.1. The change of the intensity of the time / frequency components detects the knocking vibration, the values of the determination function greatly exceed the threshold, and the knocking is clearly detected. It should be noted that although in this embodiment a case where Th = 0.1 is described as an example, the effectiveness of the invention is not limited to this value.

Second embodiment

The 5A . 5B and 5C Fig. 10 are explanatory graphs describing results of ion current-time / frequency transformation and knock determination function values in a knock detection device and a detection method according to a second embodiment of the invention. In the first embodiment, the time / frequency components were determined by a short-time Fourier transform using a Hanning window function, but in the present embodiment, the window function of Equation 6 is used to obtain a Gabor wavelet component.

[Equation 6]

• w (m) = exp (-L (m - (M-1) / 2) ² ) (6)

In the 5A . 5B and 5C For example, when Equation 6 is applied to specific data in this embodiment, the results are shown, and the state of occurrence of knocking greatly exceeds the threshold Th = 0.1 and can be determined. Thus, even in this embodiment, similar to the first embodiment, knocking is clearly detected. It should be noted that although L = 800 / (M-1) ^{2 was used} as an example of L in the above equation 6 in this embodiment, the effectiveness of the invention is not limited to this value.

In addition, a knock detection device may also include: spark plugs arranged in cylinders of an internal combustion engine; an ion current detecting means for detecting ion currents that flow in the spark plugs; a time / frequency transform means for setting time intervals allowing one or more overlaps within a time from after ignition by the spark plugs, until next fires its own cylinder or other cylinder, and for sampling current values of the ion currents in the respective ones Time intervals to determine their time / frequency components; knock detection means for detecting knock based on the time / frequency components; and detection control means for inputting a running state and for controlling the time / frequency transformation means and the knock detection means. Thus, with the knock detection device of the invention, one can grasp the distribution of a constantly changing combustion energy and can determine the knocking and precisely detect its timing.

Further, a knock detection method may further include: ion current detection means for detecting ion currents by using spark plugs arranged in cylinders of an internal combustion engine; a time / frequency transformation means for setting time intervals allowing one or more overlaps within a time from after ignition by the spark plugs until next fires a separate cylinder or cylinder thereof, and for sampling current values of the ion currents in the respective time intervals to determine their time / frequency components; knock detection means for detecting knock based on the time / frequency components; and a detection control means for controlling the time / frequency transform means and the knock detection means, wherein the detection of the knocking carried out by the detection control means, which inputs a running state of the internal combustion engine and controls the time / frequency transform means and knock detection means, to obtain from samples of the ion currents To determine time / frequency components. Thus, with the knock detection method of the invention, one can detect knock without a misdirected operation with respect to noise belonging to other time intervals, can detect knock without misdirected operation with respect to fuel in which the ion current intensity coefficients are different, and it is allows the control of an internal combustion engine according to the temporal occurrence of knocking.

Claims (10)

A knock detecting device comprising: spark plugs arranged in cylinders of an internal combustion engine; an ion current detection device ( 2 ) for detecting ion currents flowing in the spark plugs; a time / frequency transformation device ( 3 ) for sampling the ion currents at time intervals to determine time / frequency components (Cn (f)) of the sampled ion streams using a short time Fourier transform, the time intervals covering one or more intersections within a time from after ignition by one of the Allow spark plugs until next ignites a spark plug in its own cylinder or in another cylinder. A knock detecting device comprising: spark plugs arranged in cylinders of an internal combustion engine; an ion current detection device ( 2 ) for detecting ion currents flowing in the spark plugs; a time / frequency transformation device ( 3 ) for sampling the ion currents at time intervals to determine time / frequency components (Cn (f)) of the sampled ion streams using a Gabor wavelet transform, the time intervals covering one or more intersections within a time from after ignition by one of the allow the spark plugs until next ignites a spark plug in its own cylinder or in another cylinder. Knock-detecting device according to one of Claims 1 or 2, in which the knock-detecting device ( 4 ) detects the occurrence of knocking and the time course of knocking occurring. A knock detecting apparatus according to any one of claims 1 to 3, wherein said detection control means (14 5 ) changes the sampling times, the time / frequency transformation means ( 3 ) Samples ion current values in accordance with the running state of the internal combustion engine, and / or alters the number of ion current samples which serve as the default for the time / frequency transformation. A knock detecting apparatus according to any one of claims 1 to 4, wherein the insensitivity to impulse noise and ion current intensity changes indicative of knocking is increased by dividing by a standard factor (C), a knocking determination equation using the knock detecting apparatus ( 4 ). A knock detection method, comprising: detecting ion currents using spark plugs disposed in cylinders of an internal combustion engine; Setting Time Intervals (In) that One or More Intersections of Respective Time Intervals within one time from after ignition by one of the spark plugs, until next ignites a spark plug in its own cylinder or in another cylinder; Sampling current values of the ionic currents in the respective time intervals, performing a time / frequency transformation on the sampled current values of the ionic currents and determining the time / frequency components (Cn (f)) of the ionic currents; and detecting knock based on the time / frequency components of the sampled ion streams and a running state of the internal combustion engine, and controlling the time / frequency transformation to obtain the time / frequency components (Cn (f)) of the sampled ion streams using a short time To determine the Fourier transformation. A knock detection method comprising: Detecting ion currents using spark plugs disposed in cylinders of an internal combustion engine; Setting time intervals (In) allowing one or more overlaps of respective time intervals within a time from after ignition by one of the spark plugs, until next ignites a spark plug in its own cylinder or in another cylinder; Sampling current values of the ionic currents in the respective time intervals, performing a time / frequency transformation on the sampled current values of the ionic currents and determining the time / frequency components (Cn (f)) of the ionic currents; and Detecting knocking based on the time / frequency components of the sampled ion streams and a running state of the internal combustion engine, and controlling the time / frequency transformation to obtain the time / frequency components (Cn (f)) of the sampled ion streams using a Gabor To determine wavelet transformation. The knock detection method according to any one of claims 6 or 7, wherein the occurrence of knocking and the timing of the knocking occurring are detected. A pout detection method according to any one of claims 6 to 8, wherein the sampling times are changed while sampling ion current values corresponding to the running state of the internal combustion engine in the respective time intervals, and / or sampling a number of ion current samples serving as the target for the time / frequency transformation , A knock detection method according to any one of claims 6 to 9, wherein the insensitivity to impulse noise and ion current intensity changes is increased by dividing by a standard factor (C), a knocking determination equation used in the detection of knocking.

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